Thermostat



Nov. 20, 1945. w. B. GRIFFITH THERMOSTAT Filed Nov. 17, 1944 I'Yll /5 Lag Patented Nov. 20, 1945 UNITED STATES PATENT OFFICE THERMOSTAT William B. Griffith, Stone Harbor, N. J.

Application November 17, 1944, Serial No. 563,927

7 Claims.

My invention relates to improvements in thermostats for closing electrical circuits and particularly relates to circuit closers for thermostats and the like.

Devices such as thermostats, used for fire protection purposes, for closing electric circuits, sometimes fail to operate when the terminal plates have become corroded. This is partly due to the very slight increase in pressure obtainable by the thermostat, which pressure is not suiiicient for pressing the terminals together with enough force to insure a perfect electrical contact after the corrosion occurs.

The object of my invention is to provide contact plates which may be moved by a very slight pressure into engagement and insure the proper closing of the circuit.

A further object is to construct terminal plates which will engage with a sliding, or wiping, movement and forma perfect electrical Contact.

A further object is to provide terminal plates having protuberances, upon their adjacent surfaces, arranged so that the protuberances will engage with a sliding movement to form the contact between said plates.

A further object is to provide a thermostat embodying the contact terminals in a novel manner.

These together with various other novel features f construction and arrangement of the parts, which will be more fully hereinafter described and claimed, constitute my invention.

Referring to the accompanying drawing:

Fig. 1 is an enlarged vertical sectional View of a thermostat embodying my invention.

Fig. 2 is a partial transverse section on line 2--2, Fig. l.

Figs. 3 and 4 are perspective views of the. terminal plates, detached.

Fig. 5 is a view similar to Fig. 2, showing the terminal plates partially engaged when out of alignment.

Fig. 6 is a View similar to Fig. 2, showing another position of the terminal plates.

Fig. 7 is a view similar to Fig. 2, showing the terminal plates fully engaged.

In the drawing, in which like reference characters refer to like parts, 8 represents a thermostat comprising a base 9, of insulating material, upon which is a metal shell Ill, forming an air chamber I2, closed by a flexible wall, or diaphragm I3. The base 9 is provided with the usual slow leak vent I4, through which the pressure of the air within the chamber I2 may equalize with the atmosphere and a sudden rate in rise of temperature will cause the air in the chamber I2 to distend the diaphragm I3,

A terminal contact plate I5 is secured at one end thereof to the base 9 by a metal rivet I6. The plate I5 has a rectangular head Il through which the rivet I6 passes and clamps the head I1 in a rectangular recess formed in the base 9. The rivet I6 electrically connects the plate I5 with a. conductor plate I8, upon which are binding screws I9.

The terminal plate 20 is provided at one end with a head 2|, through which a rivet 22 passes and secures the head 2| Within a recess formed upon the base 9. The rivet 22 forms a conductor between the plate 20 and a conductor plate 23, upon which are binding screws 24.

Wires 25 and 26 are attached to the screws I9 and 24 and form a circuit 21, including a. source of current 28 and an alarm device 29.

The terminal plate 2D is formed of spring metal and its free end is adjustable, relatively to the plate I5, by an abutment screw 30, which is in threaded engagement with a tubular rivet 3|, secured upon the base 9.

The terminal plate I5 is formed of spring metal and may be readily flexed at the yieldable portion 33, located adjacent to the head Il, when the plate I5 is moved by the diaphragm I3 into engagement with the plate 20.

The plate I5 is provided with a rib, or boss 35, located adjacent to the center of the length of the plate I5. Said boss 35 is pressed into the thin metal plate I5 and presented toward the diaphragm I3. Said boss 35 provides a rigid portion of the plate I5 adapted to be engaged by the diaphragm.

The free end of the plate I5 is provided with a protuberance 36, having a spherical surface. Said protuberance 36 is located on the face of the plate I5 which is presented toward the adjacent face of the overlapping end of the plate 20. Said protuberance 36 is located' upon the free end of the plate I5 adjacent to the outer end of the boss 35, so that the free end of the plate I5 will be rigid between the point of engagement with the diaphragm and the protuberance 36 and said plate I5 will yield only at said iiexible portion 33.

The thermostat 8 is constructed with the terminal plate 20 and the abutment screw 30 located at a distance from the axis of the diaphragm I3, which permits the plate I5 to extend across the center of the diaphragm and the boss 35, on the medial portion of the plate I5, to engage the center of the diaphragm, where the greatest movement of the diaphragm is obtainable for moving the protuberance 36, on the free end of the plate I5, into engagement with the plate 20.

The free end of the plate 20 is provided with protuberances 31 and 38, in the form of pressed ribs, having cylindrical surfaces presented toward the protuberance 36 on the plate I5. Said protuberances, or ribs, 31 and 38 extend lengthwise of the plate 20 and in spaced parallel relation to each other, and the portion of the plate 20, between the ribs, will be flexible along the longitudinal axis of the plate 2U,

The abutment screw 30 is positioned upon the base 9 so that it willengage the plate 20 midway between the ribs 31 and 38. Said screw 30 forms a fulcrum about which the portion of the plate 20, between the ribs 31 and 3B, may be flexed, as shown in Fig. '1, by the entrance of the protuberance 36 between the cylindrical surfaces of the ribs 31 and 38.

Due to the neXibilit-y of the portion 33 of the plate I5, the protuberance 36, on said plate I5, will vary slightly from alignment with the space between the pair of protuberances, or ribs 31 and 38, on the plate 20, therefore, when the plate I5 is moved toward the' plate 20, the protuberance 36 will first engage one of the protuberances 31 or 38, as shown in Fig. 5, and then the protuberance 36 will continue to move with a sliding contact with the surface of one of the protuberances 31 or 38 into contact with the pair of protuberances on the plate 20,'as shown in Fig. 6.

A further movement f the plate I5 from the position shown in Fig. 6 to that shown in Fig. 7, will cause the protuberance 36 to slide between the protuberances, or ribs, 31 and 38, and spread them apart, as shown in Fig. '7, thus insuring a sliding contact between the engaging surfaces of the plates I and 20, for completing the circuit 21.

In operation, my novel thermostat is located in a zone subjected to iire hazard. In the event of a re the air within the' chamber I2 will expand and distend the diaphragm into engagement with the medial portion of the plate I5 and flex the plate I5 at the portion 33 and move the protuberance 36, on the rigid free end of the plate I5, into engagement with the ribs, or protuberances 31- and38 formed upon the plate 20. The novel construction of the thermostat and the terminal contact plates, as above described, will insure a perfect contact for closing the electrical circuit.

Various changes in the construction and operation of the parts of the device may be made without departing from my invention.

I claim:

l. A thermostat having a base of insulating material, an elongated exible metal terminal plate, means mounting one end of said plate upon the base, a second metal terminal plate mounted upon the base normally in overlapping spaced relation to the free end of said iirst mentioned plate, means upon the base for connecting said plates in an electric circuit, a protuberance upon one of said plates, said protuberance having a spherical surface presented toward the opposite plate, a pair of parallel ribs upon said opposite plate presented toward said protuberance, and means for moving the free end of said first plate for engaging said protuberance and said ribs for completing said circuit.

2, A thermostat having a base of insulating material, an elongated flexible metal terminal plate, means mounting one end of said plate upon the base, a second metal terminal plate mounted upon the base normally in overlapping spaced relation to the free end of the first mentioned plate, means upon the base for connecting said'plates in an electric circuit, a protuberance upon one of said plates presented toward the opposite plate, a pair of protuberances upon said opposite plate arranged in a line extending at right angles to the length of said rst plate, said protuberances forming said pair being spaced apart for engaging the rst mentioned protuberance between them, and means for moving said rst plate for engaging the surfaces of said protuberances for completing said circuit.

3. A thermostat having a base of insulating material, an elongated iiexible metal terminal plate, means mounting one end of said plate upon the base, a second metal terminal plate mounted upon the base normally in overlapping spaced relation to the free end of the rst mentioned plate, means upon the base for connecting said plates in an electric circuit, a protuberance upon one of said plates presented toward the opposite plate, a pair of protuberances upon said opposite plate, said plate upon which said pair is mounted having a flexible portion located bet-Ween the protuberances thereon to permit the protuberances forming said pair to yield upon the engagement of said rst mentioned protuberance between them, and means for moving the free end of the rst mentioned plate for slidingly engaging the surfaces of said protuberances for completing said circuit. Y

4. A thermostat having a base of insulating material, an air chamber upon said base, a diaphragm upon said chamber adapted to be distended by the expansion of air within said chamber, ilexible contact terminal plates adapted to be included in an electric circuit, means mounting said plates upon the base with their free ends presented toward each other in overlapping spaced relation, a protuberance upon one of said plates presented toward the opposite plate, a pair of protuberances upon the opposite one of said plates, and said protuberances forming said pair arranged in spaced relation to each other adapted for aligning the rst mentioned protuberance between' the adjacent surfaces of said pair for completing said circuit upon the relative movement of said plates by the action of the diaphragm.

5. A thermostat having abase of insulating material, an air chamber upon the base, a diaphragm upon said chamber adapted to be distended by the expansion of air Within said chamber, a iiexible terminal contact plate having one end thereof secured upon the base and its free end movable by the distension of the diaphragm, a secondy nexible terminal contact plate having one end thereof secured upon the base, said plates adapted to be included in an electric circuit, a protuberance upon the first mentioned plate presented toward said second plate, a pair of protuberances upon said second plate adapted to be engaged by the protuberance upon said rst plate, and an abutment upon said base adapted for engagement with said second plate adjacent to the protuberances forming said pair and forming a fulcrum about which said second plate is adapted to be flexed by the sliding engagement of the protuberance on said iii-st plate with the protuberances on said second plate for completing said circuit through the terminals when the diaphragm is distended.

6. A thermostat having a base of insulating material, an air chamber upon the base, a diaphragm responsive to the expansion of air within said chamber, terminals adapted to be included in an electric circuit, means mounting said terminals upon the base, one of. said terminals comprising an elongated plate having one end secured by said means upon the base with its free end in spaced overlapping position with the opposite terminal, a protuberance upon said opposite terminal, a protuberance upon the free end of said plate presented toward said opposite terminal, a rib upon the central portion of the length of said plate adapted for engagement by the diaphragm, said rib positioned adjacent to the protuberance on said plate for making said plate rigid between the point of engagement by the diaphragm and the free end of said plate, and said plate having a ilexible portion located between said rib and the point of support upon the base.

7. A thermostat having a base of insulating l tended by the expansion of air within said chamber, an elongated metal plate adapted to be included ln an electric circuit, means securing one end of said plate upon the base, a protuberance upon the free end of said plate, a stiffening rib located upon said plate between said protuberance and said securing means, 'said plate located upon the base with said rib positioned adjacent to the center of the diaphragm, said plate having a ilexible portion between said rib and said securing means, a second terminal plateformed of ilexible meta-1 adapted to be included in said circuit, means securing one end of said second plate upon the base, a pair of protuberances upon the free end of said second plate, and an abutment mounted upon the base for engagement with the second plate between the protuberances forming said pair for yieldingly supporting said pair when WILLIAM B. GRIFFITH. 

